The present invention relates to a buffer amplifier suitable for use as an input amplifier for an oscilloscope. The requirements for such an amplifier include a high input impedance to minimize loading the circuit being tested, high linearity and low thermal distortion to maintain signal accuracy and fidelity, a low output impedance, and a high bandwidth capability. Conventional buffer amplifier circuits employ field-effect transistor (FET) input stages to provide high input impedance, and a single bipolar transistor emitter follower output stage. However, such conventional circuits exhibit substantial signal-caused thermal transient response aberations and nonlinearity. Also, because of the limitations of FET transconductance; conventional designs suffer a loss in high frequency response.